The present invention relates to the field of anti-jackknifing devices for tractor/trailer systems. Specifically, it relates to an anti-jackknifing system that automatically engages when the tractor driver applies the tractor brakes.
The standard method for coupling a trailer and a tractor is through use of a tractor fifth wheel and trailer pin. This coupling allows the trailer to rotate freely with respect to the tractor. Because of this freedom to rotate, trailers have a tendency to rotate out of control during sudden stops or sharp turns of the tractor. This condition is known as jackknifing.
Many references to anti-jackknifing systems are known. The inventor, however, knows of none which have the unique characteristics and simplicity of the present invention. For example, U.S. Pat. No. 4,826,198 (Herbert) teaches a plural braking means, using three calipers instead of one. The central of the three calipers locks on to a control ring when the tractor brakes are applied, but does not stop rotation of the trailer. It only allows the control ring to rotate about its axis. The outer calipers engage only when sensors detect angular movement of the control ring toward either of the angular stops placed partially around the edge of the control ring. Herbert therefore teaches a detection system which only engages a caliper to stop jackknifing when a jackknifing situation has already occurred. Furthermore, the system in Herbert requires three calipers, one of which only serves to allow rotation of the control ring. This differs from the present invention in several respects. The present invention uses a single caliper instead of three calipers. This is antithetical to the teaching of Herbert. The single caliper of the present invention provides all the braking power the system needs. Application of the tractor brakes triggers an immediate response to a potentially dangerous situation. The present invention can stop a jackknifing situation as it begins.
In addition, the brake between the tractor and trailer in Herbert is not engageable at all times when coupled. Angular motion of the control ring toward the angular stops is required before the system will engage. The present invention makes an actual connection between the modified trailer pin and the brake disk mechanism brakeable at any time. This eliminates the need for multiple calipers. The actual physical connection between the modified trailer pin and brake disk mechanism allows the anti-jackknifing device to be immediately responsive to a dangerous situation.
The present invention eliminates the need for further complicated devices to enable an anti-jackknifing system. Since it uses fewer components, it is necessarily simpler and more cost effective than other anti-jackknifing systems.
U.S. Pat. No. 4,775,165 (Grovum) teaches a detection system for actuating an anti-jackknifing system. The system in Grovum is fluid actuated, using fluid actuated cylinders to move stop pins into a jackknife limiting position. Grovum teaches a system which uses orientation of the steering wheels of the tractor to the trailer to detect a jackknife condition. The present invention needs no such detection scheme. It is actuated when the tractor driver applies the tractor brakes. The means for stopping the rotation of the trailer are also different. The present invention uses a caliper system to stop rotation of the brake trailer, whereas Grovum uses stop members which extend upward from the tractor, abruptly engaging abutments which extend downward from the trailer. As in Herbert, there is also no physical connection by the anti-jackknifing system between the tractor and trailer until after a jackknife situation has been detected, and engagement is abrupt and total.
U.S. Pat. No. 4,744,581 (Cables) teaches a curved, geared tracking bar which translates circular motion of a trailer with respect to a tractor into linear motion. There is no interaction between the fifth wheel and trailer pin in Cables. The present invention, as stated above, uses an addition to the existing trailer pin in conjunction with a brake disk mechanism creating a physical connection between the trailer pin and the brake disk mechanism.
U.S. Pat. Nos. 4,455,035 (Ivony et al.), 4,494,765 (Ratsko et al.) and 4,700,966 (Hawkins et al.) use electric circuits for control systems to detect a jackknife situation. The present invention uses no such electric control system. It is actuated immediately upon application of the tractor brakes.
U.S. Pat. Nos. 4,585,248 (Miller et al.), 4,784,403 (Hawkins et al.) and 4,790,556 (Hawkins et al.) all teach the use of separate hydraulic systems to control jackknifing of a tractor/trailer combination. The present invention uses a caliper system without the need for complicated extra systems using electronics or hydraulics. By eliminating the need for added systems, the present invention reduces costs and is simpler to use, manufacture, and install than other anti-jackknifing systems.
It is an objective of this invention to provide an anti-jackknifing system which actuates immediately upon actuation of the tractor brakes. This result is desired because many prior art systems do not act to prevent jackknifing until the jackknifing situation is well underway.
It is another objective of this invention to provide an anti-jackknifing system which is effective, yet simple and relatively inexpensive.
It is a further objective of this invention to provide an anti-jackknifing system which requires no extensive modification of either the tractor or trailer.